Update names, description & representing images of applets

[Jacob-Vlijm]

Some of the applets have outdated images on Welcome (like shuffer). Other applets would benefit a name change (like Wallstreet), to make clear what it represents. Many applet descriptions would benefit using certain keywords, like "tiling" in shuffler, to make sure people's eyes would catch it if just scanning the applet's description.
This is especially more important now the number of applets has increased over time.

[fossfreedom]

Fair enough - this also would benefit with keyword search #217